Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$156.53	4.852%	$164.1248	$164.12	$164.10	$164.10
Purchase #2	$111.33	7.323%	$119.4827	$119.48	$119.50	$119.50
Purchase #3	$33.38	13.238%	$37.7988	$37.80	$37.80	$37.80
Purchase #4	$215.94	10.500%	$238.6137	$238.61	$238.60	$238.60
Purchase #5	$211.93	3.507%	$219.3624	$219.36	$219.35	$219.40
Purchase #6	$132.73	13.146%	$150.1787	$150.18	$150.20	$150.20
Purchase #7	$71.66	5.229%	$75.4071	$75.41	$75.40	$75.40
7 purchase totals =	$933.50		$1,004.9682	$1,004.96	$1,004.95	$1,005.00